Boiler Lockout When Heating On

[f1arp72]

Having installed this system just before the summer, I put all the issues I was having behind me for the summer (like temperature overshoots and boiler firing up every 10 minutes for no reason whatsoever) and have enjoyed months of simply heating my hot water without any problems.

Now we've started turning heating back on again, my boiler is locking out whenever we seem to have the heating on. I have a 13 year old Potterton Suprima 40L and yes, the PCB has been replaced (following on from the problems and appearance it made on BBC Watchdog a good few years ago).

However, my boiler is now locking out pretty much every day when we are using the heating. I "think" it seems to be when the radiators have reached room temperature and have, or are closing. For example, I'm writing this now because I just used the "Quick Action" to turn heating off and boiler locked out about 3 minutes later. I have a S-Plan system so have separate valves for HW and CH.

Annoyingly, we had a plumber here for an hour waiting for it to cut out, and it did so 5 minutes after he left !!! He's checked the pump, circulation, boiler / heat exchanger looks clean so he's basically said he has no idea what could be causing it, especially having watched boiler for an hour going through normal heat cycles.

The plumber has suggested maybe flushing the boiler to clean it as a last resort. Failing that, he's pretty much suggested replacing the boiler as it's the only thing he can suggest.

Does anyone have ANY ideas. As I said, HW on its own is fine. CH on its own, or CH with HW it locks out the boiler??

Just to add, boiler seemed to cope on old system, so it seems to be something this annoying Evohome system has introduced.

[top brake]

Having installed this system just before the summer, I put all the issues I was having behind me for the summer (like temperature overshoots and boiler firing up every 10 minutes for no reason whatsoever) and have enjoyed months of simply heating my hot water without any problems.

Now we've started turning heating back on again, my boiler is locking out whenever we seem to have the heating on. I have a 13 year old Potterton Suprima 40L and yes, the PCB has been replaced (following on from the problems and appearance it made on BBC Watchdog a good few years ago).

However, my boiler is now locking out pretty much every day when we are using the heating. I "think" it seems to be when the radiators have reached room temperature and have, or are closing. For example, I'm writing this now because I just used the "Quick Action" to turn heating off and boiler locked out about 3 minutes later. I have a S-Plan system so have separate valves for HW and CH.

Annoyingly, we had a plumber here for an hour waiting for it to cut out, and it did so 5 minutes after he left !!! He's checked the pump, circulation, boiler / heat exchanger looks clean so he's basically said he has no idea what could be causing it, especially having watched boiler for an hour going through normal heat cycles.

The plumber has suggested maybe flushing the boiler to clean it as a last resort. Failing that, he's pretty much suggested replacing the boiler as it's the only thing he can suggest.

Does anyone have ANY ideas. As I said, HW on its own is fine. CH on its own, or CH with HW it locks out the boiler??

Just to add, boiler seemed to cope on old system, so it seems to be something this annoying Evohome system has introduced.

I see this type of scenario occasionally and I am confident that your application issues can be resolved.

In order to assist you I need the following:

Pictures of the boiler cupboard showing the wireless relays and hot water transceiver
Picture of the evohome controller
Picture of the fault log
Picture of motorised valves/bypass valve/setting of bypass
Picture of the circulation pump/setting

I can then advise on what tweaks to the system you can make

The system is a great reliable system when installed and commissioned correctly

[electronicsuk]

Have you got a bypass valve or a bypass rad? Wouldn't be surprised to see it going into lockout if not.

[The EVOHOME Shop]

I would say without seeing photos that there is no bypass valve fitted and flow rate through the heat exchange is insufficient - although 'Suprima' is not the name I would associate with this boiler, having repaired and ripped out many over the years.

[f1arp72]

Hi everyone.

Thanks for your replies. I've attached photos as requested by @top brake. The wireless receivers are up high in my airing cupboard, away fro any metal pipes (the heating one is above cupboard door, the other back left of cupboard. Just to add, I am having no problems at all with regards to the system "turning on/off, HR92s responding, etc. I'm happy that the Evohome system itself is "responding as it should." Couple of errors on the log screen, but only the two of them and this has no relevance as to when I was testing system date wise (in fact, only hot water would of been on at those times. Heating was set to "Off" anyway). Bypass valve is set to about 0.5 bar

I've done some more testing which is definitely pointing towards bypass issue. The boiler seems to lockout when heating has been on, and I then select quick action to turn it off. This closes all HR92s as expected, the boiler stops heating, pump continues (as per pump overrun) but then the chances are it will lockout which I guess suggest a bypass problem. (I guess random lockouts I've seen happen when all my rooms hit temperature and HR92s have pretty much closed automatically ???)

So, can someone PLEASE EXPLAIN why the same does not happen when it's only HW. It's using the same bypass so surely I'd of had this problem during summer months with only HW

Any other suggestions?

- Could the bypass valve be clogged, dirty and therefore not opening properly?
- Plumber did suggest increasing width of pipe as it's thinner than the other pipework in my airing cupboard as you can just make out from photos. Worth a try ??

Also, I have today removed a HR82 from conservatory radiator following @electronicsuk comment about a bypass rad to see if that helps. Won't know results until I've had further chance to test, but my original question remains. Why isn't this an issue with just HW ???

Many thanks for all your help and comments.


Actuators.jpg

Valves.jpg

Controller.jpg

[paulockenden]

When the boiler is in over-run mode try fiddling with the bypass valve. You should be able to hear the water rush through as it opens. Make sure it is opening in this instance, but not if a single TRV is open. Should be easy to get the setting right, if you listen carefully.

Also, is that bypass value the right way round? hard to tell without knowing your plumbing, but make sure the arrow is in the direction of flow.

P

[The EVOHOME Shop]

Hi everyone.

Thanks for your replies. I've attached photos as requested by @top brake. The wireless receivers are up high in my airing cupboard, away fro any metal pipes (the heating one is above cupboard door, the other back left of cupboard. Just to add, I am having no problems at all with regards to the system "turning on/off, HR92s responding, etc. I'm happy that the Evohome system itself is "responding as it should." Couple of errors on the log screen, but only the two of them and this has no relevance as to when I was testing system date wise (in fact, only hot water would of been on at those times. Heating was set to "Off" anyway). Bypass valve is set to about 0.5 bar

I've done some more testing which is definitely pointing towards bypass issue. The boiler seems to lockout when heating has been on, and I then select quick action to turn it off. This closes all HR92s as expected, the boiler stops heating, pump continues (as per pump overrun) but then the chances are it will lockout which I guess suggest a bypass problem. (I guess random lockouts I've seen happen when all my rooms hit temperature and HR92s have pretty much closed automatically ???)

So, can someone PLEASE EXPLAIN why the same does not happen when it's only HW. It's using the same bypass so surely I'd of had this problem during summer months with only HW

Any other suggestions?

- Could the bypass valve be clogged, dirty and therefore not opening properly?
- Plumber did suggest increasing width of pipe as it's thinner than the other pipework in my airing cupboard as you can just make out from photos. Worth a try ??

Also, I have today removed a HR82 from conservatory radiator following @electronicsuk comment about a bypass rad to see if that helps. Won't know results until I've had further chance to test, but my original question remains. Why isn't this an issue with just HW ???

Many thanks for all your help and comments.


[ATTACH=CONFIG]583[/ATTACH]

[ATTACH=CONFIG]584[/ATTACH]

[ATTACH=CONFIG]585[/ATTACH]

Just at a glance the bypass valve is closed way too much and its attached to pipework simply too small. This is a 22mm bypass valve for a reason.

You need sufficient flow rate through the boilers heat exchanger in order for it to not overheat, hence when on hot water demand it is using 22mm pipework with very little resistance and not overheating (also return temps to boiler will be lower). Bear in mind the HR92's close first before evohome turns off the relay box, so there can be a period of a few minutes where there is insufficient flow rate and thus overheating. As you have pump overrun, there is a lack of flow causing your issue.

Hope that helps,

Richard

[f1arp72]

Just at a glance the bypass valve is closed way too much and its attached to pipework simply too small. This is a 22mm bypass valve for a reason.

You need sufficient flow rate through the boilers heat exchanger in order for it to not overheat, hence when on hot water demand it is using 22mm pipework with very little resistance and not overheating (also return temps to boiler will be lower). Bear in mind the HR92's close first before evohome turns off the relay box, so there can be a period of a few minutes where there is insufficient flow rate and thus overheating. As you have pump overrun, there is a lack of flow causing your issue.

Hope that helps,

Richard

Thanks Richard. Years ago, we used to have a standard "manual" valve but we could never get the radiator in conservatory heating up properly so a plumber added in the "automatic" valve as we have now (he didn't change bypass pipework, just the valve). As I understand this valve, it opens and closed on pressure? So we have it set about 0.5 bar so when rads are open, the flow via the normal circuit is the "easiest" route and therefore the bypass valve stays closed. When CH valve shuts off, water is forced through the bypass valve and the pressure builds forcing open the valve ?? This helped solve our original problem.

So, my question is, f I open the valve to say 0.2 bar to maybe help with my current problem, will the water not start flowing via the bypass valve when CH is on and hence reduce the pressure round the actual CH circuit, and therefore not heat up radiators as quick or efficiently ???

I definitely take your point about pipework and we did have a plumber suggest we replace it with bigger pipes. I am worried though I'll end up in situation where my conservatory radiator never heats up, although I guess with Evohome, it will at some point as all other rads will close first, but it will will mean that my conservatory will stay cold for longer though which isn't ideal !!

Your feedback would be appreciated.

Many thanks

[Fursty Ferret]

You need your boiler manual and pump curves to work out your bypass valve setting.

* says the person who bodged his as described above.

[The EVOHOME Shop]

Thanks Richard. Years ago, we used to have a standard "manual" valve but we could never get the radiator in conservatory heating up properly so a plumber added in the "automatic" valve as we have now (he didn't change bypass pipework, just the valve). As I understand this valve, it opens and closed on pressure? So we have it set about 0.5 bar so when rads are open, the flow via the normal circuit is the "easiest" route and therefore the bypass valve stays closed. When CH valve shuts off, water is forced through the bypass valve and the pressure builds forcing open the valve ?? This helped solve our original problem.

So, my question is, f I open the valve to say 0.2 bar to maybe help with my current problem, will the water not start flowing via the bypass valve when CH is on and hence reduce the pressure round the actual CH circuit, and therefore not heat up radiators as quick or efficiently ???

I definitely take your point about pipework and we did have a plumber suggest we replace it with bigger pipes. I am worried though I'll end up in situation where my conservatory radiator never heats up, although I guess with Evohome, it will at some point as all other rads will close first, but it will will mean that my conservatory will stay cold for longer though which isn't ideal !!

Your feedback would be appreciated.

Many thanks

I am unsure what you want me to suggest? There are minimum flow rates through the heat exchanger required for each and every boiler on the market. Both myself and your plumber has said the bypass pipework is insufficiently sized. If your conservatory pipework is too long/restrictive for the size of your pump, there is very little you will be able to do about this. Pump size and speed setting is something calculated at the heating design stage. Overheating is your issue here, the flow rate needs to be increased at the end of heating demand to prevent this happening.

I suggest looking at the pump speed and open the ABV more than it currently is - which is basically in the closed position.

[top brake]

as Richard has suggested simply dial open the bypass valve to a bigger setting - suggest 0.4

regarding the comms losses on the heating actuator - please provide pictures of the system overview and system devices screens in installer mode